Ultrasound Flashcards Preview

GCSE Physics OCR Gateway P4-P6 > Ultrasound > Flashcards

Flashcards in Ultrasound Deck (8)
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1
Q

What is ultrasound?

A
  • Ultrasound is sound above 20,000 Hz which is at a higher frequency than humans can hear.
  • It travels as a pressure wave containing compressions and rarefactions.
2
Q

What are compressions and rarefactions?

A

Compressions are regions of higher pressure and rarefaction are regions of lower pressure.

3
Q

The features of longitudinal sound waves are:

A
  • They can’t travel through a vacuum. The denser the medium, the faster a sound wave travels.
  • The higher the frequency or pitch, the smaller the wavelength.
  • The louder the sound, or the more powerful the ultrasound, the more energy is carried by the wave and the larger its amplitude.
4
Q

Wave vibrations

A
  • In a longitudinal wave the vibrations of the particles are parallel to the direction of the wave.
  • In a transverse wave the vibrations of the particles are at right angles to the direction of the wave.
5
Q

When ultrasound is used to break down kidney stones:

A
  • A high-powered ultrasound beam is directed at the kidney stones.
  • The ultrasound energy breaks the stones down into small pieces.
  • The tiny pieces are excreted from the body in the normal way.
6
Q

What happens when ultrasound is used in body scans?

A
  • When ultrasound is used in body scans, a pulse of ultrasound is sent into the body.
    • At each boundary between different tissues some ultrasound is reflected and the rest is transmitted.
    • The returning echoes are recorded and used to build up an image of the internal structure.
7
Q

Ultrasound can be used for body scans because:

A
  • When ultrasound is reflected from different interfaces in the body, the depth of each structure is calculated by using the formula distance = speed x time, knowing the speed of ultrasound for different tissue types and the time for the echo to returns.
  • The proportion of ultrasound reflected at each interface depends on the densities of each of the adjoining tissues and the speed of sound in the adjoining tissues.
  • If the tissues are very different (e.g. blood and bones) most of the ultrasound is reflected, leaving very little to penetrate further into the body.
  • The information gained is used to produce an image of the body scanned.
8
Q

Ultrasound is preferred to x-rays because:

A
  • It is able to produce images of soft tissues.
  • It doesn’t damage living cells.